The field of the present invention is electronic circuits. More particularly, the present invention relates to an electronic configuration for use in a radio frequency device.
Wireless devices are transforming how people work, relax, and communicate. These devices can enable convenient access to informational, educational, and entertainment data, and provide a convenient portal for worldwide communication. Some of the most popular wireless devices are portable, which benefit not only from a small footprint, but also require a consistent and robust communication link to be useful. Without the benefit of such a dependable communication link, users are unable to reasonably rely on the availability of their wireless devices.
Generally, a wireless device has a radio transceiver that communicates with other mobile devices or to a more permanent base station. Accordingly, the wireless device has an antenna that is used to both transmit and receive radio frequency signals. In particular, the antenna and wireless device are typically configured to operate on a particular range of radio frequencies, with an information signal modulated on the radio wave.
It is a particularly difficult problem to configure a wireless device to reliably and robustly receive signals in a manner that enables the information signal to be consistently demodulated and used. Several factors affect the quality of reception and the usability of the information signal. For example, the modulation signal may be subjected to physical interferences, such as buildings, that substantially attenuate the modulation signal. Further, distance from the modulation signal source also substantially attenuate the modulation signal.
The wireless device typically has an antenna that electrically couples to processing circuitry using a single-ended connection. A single ended connection is also known as an unbalanced connection. Such a single-ended, unbalanced connection provides a ground connector and a signal connector, with the signal connector transmitting all the signal information. However, such a single ended, or unbalanced, signal tends to be highly susceptible to noise, such as power supply ripple or crosstalk from other circuitry. Inducing such noise in a wireless device results in a lower signal to noise ratio, and increases the risk of losing the information signal. It is therefore desirable to use balanced signals and connections in a wireless device. However, although balanced antennas outputting balanced signals are known, the balanced antennas are generally larger than unbalanced antennas and therefore add an undesirable bulk and weight to wireless devices. Accordingly, it has not been practical to use balanced antennas on wireless devices.
Practical limitations therefore suggest the use of the single-ended antennae on wireless devices. However, it is also known that wireless devices would benefit from the use of balanced signals, as balanced signals are less susceptible to noise, for example. Accordingly, known conventional wireless devices have processing circuitry for converting the unbalanced signal to a balanced signal. In such a manner, the singled-ended antennae signal is converted to a balanced signal to enhance the efficiency and reduce susceptibility to noise.
In known wireless devices, single-ended signals are typically converted to a balanced signal using a device commonly referred to as a xe2x80x9cbalunxe2x80x9d transformer. A balun, which is an abbreviation for xe2x80x9cbalanced-unbalancedxe2x80x9d, may be arranged, for example, as a balancing transformer. The balun receives the single-ended signal and outputs a balanced signal, such as a differential signal. In the differential signal, the output signal is a function of the difference between two conductors, and is therefore less susceptible to noise or other disturbances.
Although the use of a balun in a wireless device advantageously provides balanced signals for processing, the balun is often bulky since it is not easily implemented inside on integrated circuit. The nature of the known balun device causes the balun to undesirably add size and cost to the wireless device. The balun may also cause a signal loss, which may translate into a degraded noise figure and lower performance characteristics for the wireless device.
It is therefore an object of the present invention to provide a circuit for converting an unbalanced signal to a balanced signal without the disadvantages associated with using a balun transformer.
Briefly, the present invention provides a differential conversion circuit for converting an unbalanced signal to a balanced signal. The differential conversion circuit is constructed with primarily passive components which may be arranged on an integrated circuit to minimize size and cost. The differential conversion circuit has a terminal input for receiving an unbalanced signal that is related to a communication input signal. An inductor and a resonating capacitor connect to the terminal input, and a coupling capacitor connects to the inductor. One differential output line is provided by the resonating capacitor, while the other differential output line is provided by the coupling capacitor. The output from the capacitors is thereby a pair of lines that provide a balanced differential signal which is deliverable to a balanced load.
Advantageously, the differential conversion circuit uses primarily passive components, and so does not introduce noise or other disturbances due to the use of active components. Additionally, the differential conversion circuit is constructed from only a few components, and so adds little cost to manufacturing a wireless device. Further, the differential conversion circuit is compact and easily integrated into new or existing radio frequency (rf) circuit designs.
These and other features and advantages of the present invention will be appreciated from review of the following detailed description of the invention, along with the accompanying figures in which like reference numerals refer to like parts throughout.